Binding agent for extrudable brake lining material



United States Patent" r Coy. PtyLLimited, Sydney, New South Wales, Australia, a company of New South Wales No Drawing. pplication April 13, 1955 A Serial N0. 501,187

Claims priority, application Australia April 29, 1954 2 Claims. or. 260-293 Brake lining materials or mixtures which may be formed extrusively are well known. They invariably consist in a composition of dough-like consistency composed 'the solvent creates a fire or toxic hazard, it is responsible for slow curing rates due to tenacious retention of the solvent in the composition, the extruded articles shrink while drying out, the solvent is expensive in first cost, some of it is inevitably lost during manufacture, and insofar as it is recoverable for re-use such recovery can be achieved only at considerable expense.

By this invention the foregoing disabilities are remedied by the ability to employ ordinary water as plasticiser. Some of the advantages in using water as plasticiser will be obvious, in that it is clearly extremely inexpensive, it is not worth recovering hence the recovery problem referred to above is eliminated; and, just as clearly, it-is incapable of constituting a fire or toxic risk. Less obvious advantages, revealed by experiment, show that the composition subject hereof requires a very short curing term (compared with that employing a conventional solvent) and moreover drying out of the articles is unaccompanied by appreciable shrinkage.

According to this invention a binder for an extrudable brake lining material of the kind referred to above, consists of an aqueous resin emulsion made from the ingredients (a) to (d) and in the proportion ranges thereof set forth in the following Table A.

Table A Experiment has shown that the proportions of phenol and cashew nut shell liquid, in the extreme, may be (d) Water 100% of cashew nut shell liquid and zero percent of phenol; that is, or the cashew nut shell liquid may be used by itself as the resinifying ingredient and still give a serviceable brake linking material. For preference, however, both of these ingredients are used with neither being present in any smaller proportion than one-quarter the amount of the other.

The phenol employed may comprise, in addition or instead of ordinary phenol, substituted phenols, cresols, xylenols, or mixtures of any two or more thereof in any proportions.

Paterlted Sept. 23, 1958 The-cashew nut shell liquid may be raw or it may be thickened, by use of dehydrating agents, in known manner. For preference, however, the raw liquid is first heattrcated in known manner; for example, by preheating to 250300 F. and sending it through a counter 7 water is included due to the use of formalin or other aqueous solution, the amount of water to constitute ingredient (d) above is correspondingly adjusted.

The alkaline catalyst is caustic soda or other well known resin catalyst such as caustic potash for example. The catalyst may be previously dissolved in the water of ingredient (d).

The ingredients (a) to (d) are simply mixed together, for example, in a slow speed stirrer with, for preference, a trace. of a common anti-foaming agent such as that known as D. C. 200 Fluid. The mixed ingredients are thenheated to the boiling point of the mixture (about 207 F.) and refluxed in a vessel fitted with a stirrer and a reflux condenser open to atmosphere which prevents loss of water during refluxing. The refluxing is carried out at the mentioned boiling temperature and at atmospheric pressure until the desired viscosity of the mixture is reached. The reflux time will depend on the relative proportions of the resinifying material ingredients.

For example, with a high cashew nut shell liquid content the refluxing time may be only a few minutes, where- Table B (a) Phenol 0.7541h01. ('b1)i'Hieiat treated cashew nut shell qu 0.246mo1. (c) Formalln 0.85 mol. (d) Caustic soda 1% of the combined weight of mgre weight of ingredients (a) and (b).

(a) Water Although the dominant ingredients of a brake lining material are a fibrous material and a binder as discussed above, usual friction dusts and colouring agents may be added in accordance with known practice. Typical examples of mineral fillers for inclusion in the mix are barytes, magnesium oxide, manganese dioxide, and there are many others. Any selected proportion of a thermosetting resin powder may also be added in accordance with current practice.

The fibrous material is preferably chrysotile asbestos fibre treated by usual methods of crushing and blowing to open the fibre bundles and thus facilitate mixing. The asbestos is preferably dried before incorporation with the other ingredients.

The lining material composition also includes a curing in such proportion of the agent as will approximately.

exhaust the combining potential of the resin.

The lining material ingredients, other than the binder emulsion, are first mixed together dry; if necessary, the ingredients are ground together in a hammer mill or the like before blending with the asbestos.

The mixed dry materials are then mixed with the binder resin emulsion, for example in a dough mixer type of machine. The finally mixed material is then extruded as brake lining strip which is cut to lining lengths and cured in usual manner, for example by placement in a. curing oven at 400 F. for about'two hours.

Two typical examples of brake lining mixtures using a binderresin emulsion according hereto are as setforth in the following tables C and D.

Table C Parts by weight Asbestos fibre -a----' 51.0 Friction dust 10.0 Mineral fillers are-lndhfifihfin-.. 13.

Hexamine .-.-'-'-a-- 1.5 Binder emulsion according to Table B hereof 4...... 34.25

The binder emulsion is equivalent to 24.0 parts by Weight of anhydrous resin and the water in the mixture will constitute approximately 9.3% or the weight of the mixture.

Table -D Parts -by weight Asbestos fibre -eas e -t a. a 58.2 Mineral fillers e 15.0 Coloring agent 1.0 Hexamine 1.4 Dry powdered thermosetting resin 6.4 Binder emulsion according to Table B hereof 25.5

The binder emulsion is equivalent to 18.0 parts by liqui (b) Formaldehydm weight of anhydrous resin and the water in the mixture will constitute approximately 7% of the weight of the mixture.

Although in the foregoing description, and in the following claims, reference is made to cashew nut shell liquid as being included in molecular proportions, it is not certain whether this ingredient can be assigned molecular weight. However, the proportions of cashew nut-shell liquid are not closely critical, and from experi ment, we have found that if it be assumed to have a molecular weight-of about 288, the purposes aOf the-invention will be served.

I claim:

1. A water-resin emulsion binder for extrudable, fibrous brake lining materials consisting of (a) A henol and cashew "nutshell liquid mixture wherein the latter is at least one-quarterth ainount of the former (b) A member selected from the group consisting of formaldehyde, p'araform'aldehyd'e and -furfiural 0.6 to 0.95'm0l.

1 mol.

(c an alkaline catai stmflfluu. From 0.75% to 1.25%

of the weight of (a). (d) Wate'r n From 2% to 10% of the Weight of (a).

2. A water-resin emulsion binder for extrudable fibrous brake lining materials consisting of (a) Phenol 0.754 m'ol.

(b) Heat treated cashew nut shell 1% of the combined weight of (a) and (e) Wat-eardrumHunt.-- 5 (it the combined rzrbedght of (a) and ('11.) Caustic soda References Cited in the-file of this patent UNITED STATES PATENTS 1 2,215,596 Seebach e Sept. 24, 1940 2,385,374 Rhodes Sept. 25, 1945 2,499,365 De Groote Mar. 7, 1950 2,534,607 Laher et al. Dec. 19, 1950' Cofek Feb. 19, 1952 

1. A WATER-RESIN EMULSION BINDER FOR EXTRUDABLE, FIBROUS BRAKE LINING MATERIALS CONSISTING OF 